The present invention relates to a storage system, and it particularly relates to a storage system having a power saving function for a storage device and a control method therefor.
Hitherto, a storage system has been known that includes a server and a disk array subsystem including an array of multiple hard disk drives (which will be called HDD hereinafter) for providing storage areas to the server.
The server uses the disk array subsystem for multiple applications, and one application is that the server uses the disk array subsystem for archiving. By the way, keeping the HDDs on at all times which are not frequently accessed is not preferable from the viewpoint of power saving in the disk array subsystem. Accordingly, a power saving technology called MAID (or Massive Array of Inactive Disks) is applied to the storage system. The accesses include a read request and a write request.
MAID refers to a technology that reduces the power consumption by terminating the rotation of a disk in an HDD without any data access or shutting down the power supply to an HDD in a disk array. Since a disk array that adopts MAID is controlled to only operate the HDD that requires data access, the power consumption can be reduced.
On the other hand, several power saving modes employing the MAID function according to the degree of the power saving function have been known such as a mode that shuts down the power supply to a chassis containing multiple HDDs, a mode that shuts down the power supply to an HDD and a mode that terminates the rotation of a disk in an HDD. A disk array system has also been known that includes multiple logical units with the hierarchy of degrees of the power saving function and, according to the frequency of the access request to one logical unit, moves the data stored therein to a logical unit applying a different power saving mode (JP-A-2008-90352).    Patent Document 1: JP-A-2008-90352